This section provides background information related to the present disclosure, which is not necessarily prior art.
Engine cooling systems for automobiles often use a wax motor thermostat to open and close a radiator coolant loop to control engine warmup and cooling. Such a wax motor thermostat is typically an on/off valve with a single set point that can cause rapid thermal cycling of the radiator, which may subject the radiator to undesirable stress. Having a single set point provides no control of coolant flowrate for light to moderate loads, which may lead to “hunting” in which the thermostat opens and closes as it tries to maintain equilibrium. It would therefore be desirable to have an improved thermostat that can be held partially open at various opening amounts at different temperatures, so as to avoid severe “hunting” and to avoid sending a large amount of very hot coolant to the radiator. This will advantageously reduce thermal shock on the radiator and other components, as well as provide a cost efficient way to control engine temperature without the need for sensors or control logic.